1. Field of the Invention
This invention relates to manipulation of printing blankets.
2. Discussion of Prior Art
A common means for securing an offset printing blanket onto a press cylinder employs a tensioning `lock-up` device located within the cylinder body. Employment of such a device usually necessitates a gap in the usable printing area of the cylinder and furthermore tends to promote undesirable vibration during operation of the printing press, especially at high-speed printing.
It has been proposed to avoid vibration by providing a `seamless` or endless blanket on the printing press cylinder. Typically such blankets are supplied on a metal sleeve to be fitted on the cylinder. Although such blankets may be feasible for newly manufactured presses wherein means for ease of removal of the cylinder or sleeve may be incorporated in the design of the press, they are not a practicable option for the majority of existing presses. Moreover, a disadvantage of such blankets is the high cost of producing individual blanketed sleeves or cylinders in comparison with the cost of producing a sheet-form (open-ended) blanket for application to replace a worn or damaged similar blanket on an existing cylinder in the press.
In some relatively small offset printing presses (such as those used for printing stationery and business forms), in which the printing cylinder typically has a circumference of the order of 30 cm, a negligible gap in the usable printing area is achieved by securing a sheet-form printing blanket on the cylinder by means of an adhesive which typically is in the form of an adhesive coating on the back of the blanket sheet and may be protected by a releasable cover sheet until the blanket is applied to the cylinder.
Although adhesive-backed printing blankets are used for small presses, generally they have not been used for large web-feed printing presses owing to problems in handling and mounting large sheets of adhesive-backed blanket. Problems include manual handling difficulties and safety risk to persons manipulating a bulky adhesive-backed blanket, the risk of contamination of the adhesive backing during manipulation, and the need for the initial positioning of the blanket on the cylinder to be accurate since the capability for position-adjustment after initial application usually is extremely limited or non-existent without detriment to the blanket or the adhesive bond.
In large high-speed printing presses, such as those used in the newspaper and magazine printing industry, typically the printing blanket requires to be replaced owing to wear at frequent intervals, for instance every one to three months. Speed of application of a replacement blanket onto the cylinder is especially important in the newspaper and magazine printing industry where a long down-time of a printing press could be highly detrimental to meeting distribution deadlines.